JP5142950B2 - Array antenna - Google Patents

Description

  The present invention provides a linear subarray having a plurality of element antennas arranged in a direction perpendicular to a main beam scanning plane, a feeder circuit connected to the plurality of element antennas, and a phase shifter connected to the feeder circuit. The present invention relates to an array antenna configured to be arranged in a rectangular shape defined by an X direction perpendicular to a beam scanning direction and a Y direction parallel to the beam scanning direction.

  Array antennas are often used as antennas for radar devices or radio wave monitoring devices. Such an array antenna is required to have a larger antenna gain as antenna performance in order to detect a farther target or to detect weaker radio waves.

  Since the antenna gain is proportional to the aperture diameter of the antenna, it is necessary to increase the antenna diameter to obtain a larger antenna gain.

  In the array antenna, if the element antenna spacing is such that no grating lobe is generated, the element spacing cannot be increased. As a result, as the aperture diameter increases, the number of element antennas increases, and the number of phase shifters connected to the element antennas also increases. In general, phase shifters are expensive, and it is desirable to suppress the number of phase shifters in the entire antenna. Thus, it has been considered to reduce the number of phase shifters by combining several element antennas into subarrays and providing a phase shifter for each subarray (see, for example, Patent Document 1).

  In such a configuration, the unit for controlling the phase by the phase shifter is changed from the element antenna to the subarray. Therefore, in order to prevent the generation of grating lobes, it is necessary to provide a space between the centers of the subarrays. However, since the size of the element antenna is about a wavelength, it is difficult to set the center interval of the subarrays including the element antennas to one wavelength or less, and there is a problem that a grating lobe occurs.

  Generation of the grating lobe reduces the antenna gain in the desired direction and receives incoming radio waves from directions other than the desired directivity direction. As a result, ambiguity occurs in the direction detection. Therefore, a configuration for avoiding the generation of grating lobes while reducing the number of phase shifters connected to the element antenna is desired.

  In such a situation, a technique for reducing ambiguity due to grating lobes by arranging antennas at unequal intervals as the interval between array antennas having no periodicity is disclosed (for example, Patent Document 2, Non-Patent Document 1) reference).

  Further, as a polygon arrangement method having no periodicity, a technique has been proposed in which a grating lobe is suppressed over a wide band by selecting a Penrose tile, an octagonal, a table, etc., and arranging an element antenna at the apex position (for example, Non-Patent Documents 2 and 3).

JP-A-5-291814 JP 2005-257384 A IEICE Transactions B Vol. J83-B No. 6 pp. 845-851 “Direction estimation using non-uniformly spaced arrays” Vincenzo Pierro et. Al. “Radiation Properties of Planar Antenna Arrays Based on Certain Categories of Aperiodic Tilings” IEEE TRANSACTION ON ANTENNAS AND PROPAGATION, vol.53, NO.2, pp.635-644, Feb 2005 Glassner, A. “Penrose tiling”, IEEE Computer Graphics and Applications, vol.18, Issue4, pp.78-86, July / Aug 1988

However, the prior art has the following problems.
As a method for reducing the grating lobe, the intervals between the element antennas are assumed to be unequal. Here, for example, when the interval between the element antennas is set at random, there is a problem in that the feeding system connected to the element antenna becomes complicated because there is no periodicity. Furthermore, there has been a problem that the manufacturing cost of the antenna increases due to the fact that the product is a small variety of products.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain an array antenna that suppresses grating lobes and suppresses an increase in manufacturing cost.

An array antenna according to the present invention includes a linear subarray having a plurality of element antennas arranged in a direction perpendicular to a main beam scanning plane, a feed circuit connected to the plurality of element antennas, and a phase shifter connected to the feed circuit. Are arranged in a rectangular shape defined by an X direction perpendicular to the beam scanning direction and a Y direction parallel to the beam scanning direction, the linear subarray has an X direction dimension a, a Y direction dimension b, A linear array consisting of n elements, with linear subarrays arranged in the Y direction in the same cycle, arranged in I rows (I is an integer greater than or equal to 1) in the X direction is a unit linear array, and W unit linear arrays are arranged in the X direction. (W is an integer of 1 or more) are arranged to form a rectangular array, and the same period in each unit linear array is T (w) (w is 1 or more and W or less). ), And the amount of deviation in the Y direction between the linear array of the first row and the linear array of the i-th row (i is an integer of 1 to I) in each unit linear array is ΔZ (w, i) Where a constant commonly set for all unit linear arrays is α (0 <α ≦ 1), T (w) = b + α (w−1) b / W (w = 1, ... W)
ΔZ (w, i) = (i−1) T (w) / I (i = 1,..., I)
Thus, the period T (w) in each unit linear array and the shift amount ΔZ (w, i) of each row in each unit linear array are determined, and a rectangular array is specified.

  According to the present invention, a linear array in which linear subarrays having the same shape are arranged with a specific period are shifted and arranged to design and manufacture a linear subarray of the same design and a plurality of types of linear arrays, thereby reducing manufacturing costs. However, it is possible to obtain the same grating lobe suppression effect as in the case where the elements are randomly arranged, and to obtain an array antenna that suppresses the grating lobes and suppresses an increase in manufacturing cost.

  Hereinafter, preferred embodiments of the array antenna of the present invention will be described with reference to the drawings. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing a configuration of a unit linear array which is a part of an array antenna according to Embodiment 1 of the present invention. The respective symbols in FIG. 1 mean the following.
1: Element antenna 2: Feeding circuit connected to element antenna 1 3: Phase shifter connected to feeding circuit 2 4: Linear subarray 5: Linear array

  In FIG. 1, the main beam scanning direction is the Y direction, and the direction orthogonal to the beam scanning direction is the X direction. An element antenna 1 having four elements arranged in the X direction, one feeding circuit 2 and one phase shifter 3 constitute one linear subarray 4. Further, the linear subarray 4 is defined by a dimension in the X direction orthogonal to the beam scanning direction and b dimension in the Y direction parallel to the beam scanning direction.

  The linear array 5 is composed of one row of linear subarrays 4 in which the linear subarrays 4 are arranged in the Y direction at the same period (corresponding to T (w) in FIG. 1). Further, a linear array 5 having such a configuration in which a plurality of rows (three rows in FIG. 1) are arranged in the X direction is used as a unit linear array.

  An array antenna having a rectangular array is configured by arranging a plurality of unit linear arrays shown in FIG. 1 in the X direction. Here, the outer dimension of the array antenna in the X direction orthogonal to the beam scanning direction is A, and the outer dimension of the array antenna in the Y direction parallel to the beam scanning direction is B. Further, as described above, the dimension in the X direction of the linear subarray 4 is a, the dimension in the Y direction is b, and the number of elements in the linear subarray 4 is n.

Further, when a rectangular array is formed by arranging W unit linear arrays in the X direction (W is an integer of 1 or more), the following symbols are further defined.
T (w): A period common in the w-th unit linear array and adjacent to the Y direction.
Corresponds to the relative distance of the near subarray 4 (w is an integer between 1 and W)
I: Common to all unit linear arrays, and the number of rows of the linear array constituting the unit linear array (I is an integer of 1 or more)
M (w): The linear subarray 4 has the same period in the wth unit linear array.
Number of columns when arranged in the Y direction at T (w) ΔZ (w, i): the first row linear array and the i th row in the w th unit linear array
Deviation in the Y direction from the linear array (where i is an integer between 1 and I)
Quantity α: A constant (0 <α set in common to all unit linear arrays to define the array)
≦ 1)

In this case, the rectangular array of the array antenna is specified by the following expressions (1) and (2).
T (w) = b + α (w−1) b / W (w = 1,..., W) (1)
ΔZ (w, i) = (i−1) T (w) / I (i = 1,..., I) (2)

At this time, in order for the linear array to be within the opening surface, I and M (w) must satisfy the following expressions (3) and (4).
I ≦ {A / (a × W)} (3)
M (w) ≦ B / T (w) − {1- (1 / I)} (4)

FIG. 2 is an exemplary diagram showing a specific arrangement of the linear subarray 4 in the array antenna according to the first embodiment of the present invention. In FIG. 2, each parameter is set as follows. Where λ is a wavelength.
A = B = 20λ
a = λ
b = 1.5λ
n = 2
W = 4
α = 1

And using the above formulas (1) to (4), I and M (1) to M (4) are set as follows.
I = 5
M (1) = 12
M (2) = 9
M (3) = 8
M (4) = 6

  In the case of the array antenna having the arrangement of FIG. 2, it was confirmed by numerical calculation that the grating lobe level is improved by 10.13 dB.

  As described above, according to the first embodiment, all the linear subarrays have the same functions and dimensions, and therefore can be manufactured under one kind of design and manufacturing conditions. Furthermore, the design of a linear array in which linear subarrays are arranged in the Y-axis direction can be manufactured under W design and manufacturing conditions, and the position can be shifted when the array is configured. For this reason, it is possible to suppress the same grating lobe while reducing the manufacturing cost of the array antenna as compared with the conventional random array.

Embodiment 2. FIG.
In the array antenna having the configuration of FIG. 2 of the first embodiment, linear arrays having the same period are adjacent to each other. For this reason, local periodicity remains in an oblique direction, which prevents grating lobe suppression. Therefore, in the second embodiment, an arrangement of linear subarrays 4 for canceling such periodicity will be described.

  FIG. 3 is an exemplary diagram showing a specific arrangement of the linear subarray 4 in the array antenna according to the second embodiment of the present invention. In the arrangement of FIG. 2 in the first embodiment, since I = 5 and W = 4, a linear array having the same period is adjacent. On the other hand, in the arrangement of FIG. 3 in the second embodiment, I = 1 and W = 20 so that the periods of adjacent linear arrays are not the same.

  Although not shown, the periodicity can be canceled by changing the order in the Y direction in units of one row so that linear arrays having the same period are not adjacent to each other in the arrangement shown in FIG. is there.

  By canceling the periodicity using these methods, the grating lobes are dispersed and suppressed in the direction orthogonal to the scanning plane.

  As described above, according to the second embodiment, by adopting an arrangement that cancels the periodicity so that linear arrays having the same period are not adjacent to each other, in addition to the effects in the first embodiment, further suppression of grating lobes can be achieved. It becomes possible.

Embodiment 3 FIG.
In the first and second embodiments, the rectangular array antenna has been described. In the third embodiment, a case will be described in which the present invention is basically applied to an array antenna having a circular or polygonal antenna outline while using this rectangular array.

  FIG. 4 is an exemplary diagram showing a specific arrangement of the linear subarray 4 in the array antenna according to the third embodiment of the present invention. The array antenna 7 in FIG. 4 is an array antenna having a rectangular array by the method described in the first and second embodiments. On the other hand, the array antenna 6 in FIG. 4 has a circular or polygonal antenna outer shape, and after the array antennas 7 are arranged in a rectangular shape, a linear subarray included in the desired outer shape is selected. Realized.

  As described above, according to the third embodiment, a desired one is selected from the linear subarrays arranged in a rectangular shape, and an array antenna having a circular or polygonal antenna outer shape is configured. The same effects as those of the first and second embodiments can be obtained.

It is a perspective view which shows the structure of the unit linear array which is a part of array antenna which concerns on Embodiment 1 of this invention. It is the exemplary diagram which showed the specific arrangement | sequence of the linear subarray in the array antenna of Embodiment 1 of this invention. It is the illustration figure which showed the specific arrangement | sequence of the linear subarray in the array antenna of Embodiment 2 of this invention. It is the illustration figure which showed the specific arrangement | sequence of the linear subarray in the array antenna of Embodiment 3 of this invention.

Explanation of symbols

  1 element antenna, 2 feeder circuit, 3 phase shifter, 4 linear subarray, 5 linear array, 6, 7 array antenna.

Claims (4)

A linear sub-array having a plurality of element antennas arranged in a direction perpendicular to a main beam scanning plane, a feeding circuit connected to the plurality of element antennas, and a phase shifter connected to the feeding circuit is provided in the beam scanning direction. In an array antenna configured to be arranged in a rectangular shape defined by a vertical X direction and a Y direction parallel to the beam scanning direction,
The linear subarray is composed of an X-direction dimension a, a Y-direction dimension b, and the number of elements n.
A linear array in which the linear sub-arrays are arranged in the Y direction at the same period, and a unit linear array in which I rows (I is an integer of 1 or more) are arranged in the X direction,
The unit-shaped linear array is arranged in the X direction by arranging W (W is an integer of 1 or more) to form the rectangular array,
The same period in each unit linear array is T (w) (w is an integer not less than 1 and not more than W), and the first row linear array and the i-th row (i is an integer not less than 1 and not more than I) in each unit linear array. And the constant set in common to all unit linear arrays in order to define the array as α (0 <α ≦ 1) (1) (2)
T (w) = b + α (w−1) b / W (w = 1,..., W) (1)
ΔZ (w, i) = (i−1) T (w) / I (i = 1,..., I) (2)
To determine the period T (w) in each unit linear array and the shift amount ΔZ (w, i) of each row in each unit linear array, and specify the rectangular array. The array antenna according to claim 1, wherein
An array antenna characterized in that the arrangement of the linear array in the first row of each unit linear array in the X direction is determined such that the grating lobes are dispersed and suppressed in a direction orthogonal to the scanning plane. The array antenna according to claim 1 or 2,
An array antenna characterized by finally identifying the rectangular array by changing the order of the rows of a linear array of (I × W) rows. The array antenna according to any one of claims 1 to 3,
An array configured by selecting a linear subarray included in a desired outer shape having a circular or polygonal antenna outer shape from among the linear subarrays included in the specified rectangular array. antenna.

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